U.S. Pat. Nos. 5,392,338 and 4,658,417 set the standard method of inputting an alphabet via the phone keypad, in which pushing a button one or more times during some period enters a character. The method is simple and easy to learn but is slow and limited in the number of characters.
The most promising system to bypass the disadvantages of the above multipress method is the two-key system, in which each character is entered via two buttons, pressed simultaneously or sequentially. Typewriter and computer keyboards have always used the two-key system. Capitalization, for example, is accomplished by simultaneously pressing a shift button and another button. Most computer applications support control actions on simultaneously pressing a control button and another button, and many also allow menu selection by sequentially pressing an alt button and then typing another button. The two-key system is also used to input non-English letters in some languages.
People have patented many variations of the two-key systems on small keyboards, such as U.S. Pat. Nos. 6,847,706; 6,802,661; 6,765,556; 5,392,338; 5,339,358; 5,117,455; 4,658,417; 3,967,273, all of which are incorporated herein by reference.
All patents, patent applications, provisional applications, and publications referred to or cited herein, or from which a claim for benefit of priority has been made, are incorporated herein by reference in their entirety to the extent they are not inconsistent with the explicit teachings of this specification.